Well, let's look at this way; she created and influenced Sith, even if you didn't believe she was a candidate of Sidious.

She also, in an out of universe article, completed Lumiya's Sith training and made her a true apprentice.

I believe she was Sidious' candidate, which certainly gives her a better claim to the Sith throne than Lumiya, who was one of the two candidates of the apprentice... she was nothing until she beat Flint.

Vergere is a grey Force-user. I hesitate to call her either a Jedi or Sith. She has her own philosophy and to hell with everyone else. I don't think she was ever trained as a Sith or part of the elite Sith club that's hidden on Korriban.

Vergere has always been a pretty interesting character to me. In a lot of ways she reminds of an anarchist, in that she inspires galactic dissonance, but at the same time, she does seem motivated by a specific purpose. The fact that her machinations tended to support a Sith endgame, I'd say tentatively yes. However, I feel like a more apt description would make her an evil puppeteer.

I always believed that Lumiya was lying about Vergere. She wanted to get back at Luke and the best way to do it? Corrupt his nephew.

Or his son. I have little doubt revenge was involved, but if she did lie about Vergere, did it matter? She was right about Vergere in that she would have learned Sith ways and passed through them. No boundaries for that Fosh.

Vergere has always been a pretty interesting character to me. In a lot of ways she reminds of an anarchist, in that she inspires galactic dissonance, but at the same time, she does seem motivated by a specific purpose. The fact that her machinations tended to support a Sith endgame, I'd say tentatively yes. However, I feel like a more apt description would make her an evil puppeteer.

Agreed. There are Force users who are beyond Jedi and Sith. Revan. Kreia, Vergere. Jacen.

Vergere's machinations are just that; machinations for the sake of it. She's fostering conflict for conflicts sake, in my mind.